The present invention relates to illuminated signs, and in particular to a lens stripe for collimating light from an array of light emitting diodes to illuminate display board and opaque types of signs.
Most light emitting diodes (LED""s) transmit light in the axial direction of the LED within a certain viewing angle, 360 degrees symmetrically around the LED axis. This type of emission pattern is easiest and least costly to manufacture. Thus, most LED lamps or signs employing LED""s are designed with the LED""s facing out from the face of the sign to emit light away from the sign surface.
LEDs are not presently suitable for many other sign applications. For example, display board signs are made of a transparent or hallow material, whereby light is coupled into the sign through one or more of its side edges. The light travels through the interior of the display board and is diffused out through its front and/or back faces. However, it is difficult to efficiently couple light from LEDs into display board signs, let alone evenly illuminate such signs with LEDs. The diverging LED output tends to brightly illuminate only that portion of the display board closest to the LEDs, thus requiring additional LEDs to adequately illuminate the darkest portions of the sign. Some diverging light from the LED""s is not even coupled into the sign, which represents wasted light. Some prior art devices attempt to alleviate such problems by using oval LED lamps with narrower viewing angles, or by shaping the sign with a reducing thickness as the light travels through the sign, or by mounting LED""s along all four edges, as illustrated in U.S. Pat. Nos. 6,023,869; 5,950,340; and 6,027,235. But, these solutions are complex, expensive, increase energy consumption and achieve only limited success in maximizing coupling efficiency and illumination consistency.
Another example of a sign application for which standard LEDs are not suitable are standard illuminated opaque highway signs. These signs have a front sign plate that is typically illuminated by lights mounted in front of the sign and oriented to direct light back onto the front sign plate. The lights are typically turned on all night, and thus use significant amounts of electricity. LED""s are more energy efficient that standard lights, but LEDs are not used to illuminate such signs because of the diverging light output, the cost of using inefficient LEDs, or complexity and inefficiency of using oval LED lamps.
There is a need for an LED design that efficiently couples the light generated by LEDs into the sign (or onto the sign plate) to evenly illuminate display board and opaque signs with the fewest possible LEDs.
The present invention solves the aforementioned problems by providing a lens stripe that efficiently couples light generated by LEDs into display board or opaque signs. The lens stripe easily attaches to the LED arrays or supporting printed circuit boards, and has a simple design that efficiently directs light to the sign, reduces cost of production, and increases energy efficiency.
The present invention is a focused linear array of light emitting diodes for illuminating a sign, which includes a linear array of light emitting diodes (LEDs) for producing a light output, and an elongated lens stripe. The linear array of LEDs includes an elongated mounting member and a plurality of LEDs mounted along a length of the mounting member. The elongated lens stripe is attached to the linear array of LEDs, and includes a reflector portion and a lens portion. The reflector portion has two elongated and opposing side walls that form an elongated channel. The side walls are light reflective, wherein the LEDs are disposed inside the channel such that the side walls reflect the light output from the LEDs toward an elongated open end of the channel. The lens portion has an elongated lens disposed along the open end of the channel for focusing the light output from the LEDs onto the sign.
In another aspect of the present invention, an illuminated sign includes a sign and a focussed linear array of light emitting diodes. The sign has a front face, a rear face and a side edge. The focussed linear array of light emitting diodes (LEDs) produces a light output for illuminating the sign, and includes an elongated mounting member, a plurality of LEDs mounted along a length of the mounting member, and an elongated lens stripe attached to at least one of mounting member and LEDs. The lens stripe includes a reflector portion having two elongated and opposing side walls that form an elongated channel, and a lens portion. The channel side walls are light reflective, wherein the LEDs are disposed inside the channel such that the side walls reflect the light output from the LEDs toward an elongated open end of the channel. The lens portion has an elongated lens disposed along the open end of the channel for focusing the light output from the LEDs onto the sign to evenly illuminate the sign.
In yet another aspect of the present invention, an illuminated sign includes a sign and a focussed linear array of light emitting diodes. The sign has a front face, a rear face and a side edge. The focussed linear array of light emitting diodes (LEDs) produces a light output to illuminate the sign, and includes an elongated mounting member, a plurality of LEDs mounted along a length of the mounting member, and an elongated lens stripe attached to at least one of mounting member and LEDs. The lens stripe includes a reflector portion having two elongated and opposing side walls that form an elongated channel. The side walls are light reflective and the LEDs are disposed inside the channel. The side walls have a non-planar shape for reflecting and focusing the light output from the LEDs onto the sign to evenly illuminate the sign.
Other objects and features of the present invention will become apparent by a review of the specification, claims and appended figures.